I agree with Mr X on everything. Powder Blues and Clown Tangs can be very aggressive.
As for order, I would think Cardinals first and next, Butterflies. Butterflies are tricky and I've never had luck with them. Like with Tangs, adding at the same time is a good idea. Not sure how the will do with all the Tangs eventually...Clowns towards the middle of the list. Rabbit fish next and Tangs last.
I'd QT before adding. It would stink to get all those fish in there and have the Tangs introduce Ich into the DT. It could come from any of them, but playing the odds, it will be the Tangs at the end.